AD51B in Familial Breast Cancer

Common variation on 14q24.1, close to RAD51B, has been associated with breast cancer: rs999737 and rs2588809 with the risk of female breast cancer and rs1314913 with the risk of male breast cancer. The aim of this study was to investigate the role of RAD51B variants in breast cancer predisposition, particularly in the context of familial breast cancer in Finland. We sequenced the coding region of RAD51B in 168 Finnish breast cancer patients from the Helsinki region for identification of possible recurrent founder mutations. In addition, we studied the known rs999737, rs2588809, and rs1314913 SNPs and RAD51B haplotypes in 44,791 breast cancer cases and 43,583 controls from 40 studies participating in the Breast Cancer Association Consortium (BCAC) that were genotyped on a custom chip (iCOGS). We identified one putatively pathogenic missense mutation c.541C>T among the Finnish cancer patients and subsequently genotyped the mutation in additional breast cancer cases (n = 5259) and population controls (n = 3586) from Finland and Belarus. No significant association with breast cancer risk was seen in the meta-analysis of the Finnish datasets or in the large BCAC dataset. The association with previously identified risk variants rs999737, rs2588809, and rs1314913 was replicated among all breast cancer cases and also among familial cases in the BCAC dataset. The most significant association was observed for the haplotype carrying the risk-alleles of all the three SNPs both among all cases (odds ratio (OR): 1.15, 95% confidence interval (CI): 1.11–1.19, P = 8.88 x 10−16) and among familial cases (OR: 1.24, 95% CI: 1.16–1.32, P = 6.19 x 10−11), compared to the haplotype with the respective protective alleles. Our results suggest that loss-of-function mutations in RAD51B are rare, but common variation at the RAD51B region is significantly associated with familial breast cancer risk

Kava Lactones and the kava-kava controversy

Kava-kava is a traditional beverage of the South Pacific islanders and has had centuries of use without major side effects. Standardised extracts of kava-kava produced in Europe have led to many serious health problems and even to death. The extraction process (aqueous vs. acetone in the two types of preparations) is responsible for the difference in toxicity as extraction of glutathione in addition to the kava lactones is important to provide protection against hepatotoxicity. The Michael reaction between glutathione and kava lactones, resulting in opening of the lactone ring, reduces the side effects of the kava kava extracts. This protective activity was demonstrated using Acanthamoebae castellanii in which 100% cell death occurred with 100 mg ml-1 kava lactones alone, and 40% cell death with a mixture of 100 mg ml -1glutathione and 100 mg ml -1 kava lactones. A comparison of kava lactone toxicity with other pharmaceutical products is discussed and recommendations made for safe usage of kava-kava product

Methyl DNA adducts, DNA repair, and hypoxanthine-guanine phosphoribosyl transferase mutations in peripheral white blood cells from patients with malignant melanoma treated with dacarbazine and hydroxyurea

Dacarbazine (DTIC) is a DNA-methylating drug used in the treatment of malignant melanoma. Among the DNA dducts induced by DTIC are N7-methylguanine (N7-meG) and O6-methylguamne (O6-meG). The latter adduct, in particular, may be important in the mutagenic as well as the cytotoxic activity of DTIC. Repair of O6-meG is carried out by the enzyme O6-alkylguanine-DNA-alkyltransferase (AGT) by a process which results in its autoinactivation. N7-meG is lost from DNA partly spontaneously and partly by enzymatic depurination followed by excision repair of the resulting apurinic site. The purpose of this study was to determine the in vivo kinetics of formation and repair of O6-meG and N7-meG and the changes in AGT in peripheral WBCs with repeated doses of DTIC, and to determine the effects on these processes of concomitant administration of hydroxyurea. In addition, we examined the induction of mutations at the HPRT gene locus. Thirty-four patients with malignant melanoma received 1.0 g/m2 DTIC i.v. every 3 weeks. Hydroxyurea was added to the second and subsequent doses of DTIC in 19 patients. The concentrations of O6-meG, N7-meG, and AGT in peripheral blood lymphocytes were determined up to 24 h after each of the first two doses of DTIC. Mutations at the HPRT gene locus were determined using the T-cell clonal assay. Peak O6-meG levels were detected 1 and 4 h after the first and second dose of DTIC, respectively. AGT concentrations declined to 56.7% (range, 40.3-76.9%) and 55.0% (range, 45.4-58.9%) of pretreatment levels 24 h after the first and second doses of DTIC, respectively, and were still approximately 25% below their initial levels just prior to administration of the second dose of DTIC. An increase in formation of O6-meG was observed at all time points after the second dose of DTIC (P = 0.0001), which was not affected by cotreatment with hydroxyurea (P > 0.5). There was a negative correlation between pretreatment AGT levels and the O6-meG concentration at 24 h after therapy (r = -0.554, P = 0.014). N7-meG levels peaked at 6 h after DTIC therapy and were not significantly influenced by the cycle number. Cotreatnient with hydroxyurea tended to be associated with lower levels of N7-meG (P = 0.08). There was no correlation between either O6-meG or N7-meG levels and the grade of neutropenia. On the basis of a limited series of blood samples analyzed, there was no firm evidence that chemotherapy with DTIC resulted in induction of HPRT mutations in lymphocytes. In conclusion, repeated administrations of DTIC resulted in higher concentrations of O6-meG, probably due to reduction in cellular AGT. Hydroxyurea did not significantly influence the kinetics of O6-meG, and N7-meG adduct formation. There was no significant induction of HPRT gene mutations with DTIC. This study suggests that sequencing of DTIC doses should be evaluated using the time course of cellular AGT depletion and DNA adduct formation to achieve higher cytotoxic efficiency. Chemicals/CAS: 7-methylguanine, 578-76-7; Dacarbazine, 4342-03-4; DNA Adducts; Guanine, 73-40-5; Hydroxyurea, 127-07-1; Hypoxanthine Phosphoribosyltransferase, EC 2.4.2.8; O(6)-Methylguanine-DNA Methyltransferase, EC 2.1.1.63; O-(6)-methylguanine, 20535-83-

Identification and antimicrobial susceptibility of bacteria isolated from corneal ulcers of dogs Identificação e susceptibilidade antimicrobiana de bactérias isoladas de úlceras de córnea em cães

A total of 22 clinical specimens were obtained from 19 dogs with corneal ulcer (16 unilateral and three bilateral) for isolation and antimicrobial susceptibility evaluation of the isolated bacteria. Bacterial growth was observed in 100% of the samples (n=22). Staphylococcus intermedius was the predominant species (35.5%), followed by Corynebacterium xerosis (19.3%). Gentamicin, ciprofloxacin, chloramphenicol and tobramycin had a high efficacy against all of the isolated bacteria. The results evidenced that 80.7% of the isolates were Gram positive cocci and Gram positive bacilli, and that those microorganisms were sensitive to gentamicin, ciprofloxacin, chloramphenicol and tobramycin.<br>Utilizaram-se 22 amostras de material, obtidas de 19 cães com úlcera de córnea, sendo 16 unilaterais e três bilaterais, para isolamento e avaliação da susceptibilidade antimicrobiana das bactérias isoladas. Observou-se crescimento bacteriano em 100% das amostras (n=22). A espécie predominante foi Staphylococcus intermedius (35,5%) seguido de Corynebacterium xerosis (19,3%). Gentamicina, ciprofloxacina, cloranfenicol e tobramicina apresentaram alta eficácia contra todas as bactérias isoladas. Os resultados evidenciam que 80,7% dos isolados foram cocos e bacilos Gram positivos e que estes microrganismos foram sensíveis à gentamicina, ciprofloxacina, cloranfenicol e tobramicina